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In all areas of special flood hazards where base flood elevation data has been provided, the following provisions are required:
(a) Residential construction. New construction and substantial improvement of any residential structure shall have the lowest floor (including basement), elevated two feet above the base flood elevation. A registered professional engineer, architect, or land surveyor shall submit a certification to the floodplain administrator that the standards of this chapter are satisfied.
(1) Site plans for new residential structures are required to specify the minimum ground elevation (MGE) which designates the elevation of the top of the black dirt under the grass, or the top of the landscape rock or other landscape material at the lowest exposed part of the house.
(2) Exception: Structures on areas removed from areas of special flood hazard with a FEMA-approved LOMR-F may proceed with construction per standards listed in FEMA Technical Bulletin 10-01, Ensuring That Structures Built on Fill In or Near Special Flood Hazard Areas Are Reasonably Safe From Flooding.
(3) Structures on areas removed from areas of special flood hazard with a FEMA-approved LOMR-F, and per the community acknowledgment form submitted with Letter of Map Change, shall have elevation drawings at the time of application for a building permit and must be signed and sealed by a licensed professional engineer or surveyor.
The professional is verifying that no new construction or substantial improvement is allowed unless the lowest floor elevation is two feet or more above the BFE. The elevation drawing shall include the following:
A. Lowest floor elevation (including basement);
B. The lowest ground elevation touching the building (entry point); and
C. Base flood elevation.
(b) Nonresidential construction. New construction and substantial improvements of any commercial, industrial, or other nonresidential structure shall have the lowest floor (including basement) elevated two feet above the base flood level. A registered professional engineer or architect shall develop and/or review structural design, specifications, and plans for the construction and shall certify that the design and methods of construction are in accordance with accepted standards of practice as outlined in this section.
(c) Enclosures. New construction and substantial improvements with fully enclosed areas below the lowest floor that are usable solely for parking of vehicles, building access, or storage in an area other than a basement and which are subject to flooding shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or meet or exceed the following minimum criteria:
(1) A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided;
(2) The bottom of all openings shall be no higher than one foot above grade; and
(3) Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
(d) Manufactured homes.
(1) Require that all manufactured homes to be placed within Zone A on a community’s FHBM or FIRM shall be installed using methods and practices which minimize flood damage. For the purposes of this requirement, manufactured homes must be elevated and anchored to resist flotation, collapse, or lateral movement. Methods of anchoring may include, but are not limited to, use of over-the-top or frame ties to ground anchors. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces.
(2) Require that manufactured homes that are placed or substantially improved within Zones A1-30, AH, and AE on the community’s FIRM on sites:
A. Outside of a manufactured home park or subdivision;
B. In a new manufactured home park or subdivision;
C. In an expansion to an existing manufactured home park or subdivision; or
D. In an existing manufactured home park or subdivision on which a manufactured home has incurred “substantial damage” as a result of a flood, be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated two feet above the base flood elevation, and be securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.
(e) Recreational vehicles.
(1) Require that recreational vehicles placed on sites within Zones A1-30, AH, and AE on the community’s FIRM either:
A. Be on the site for fewer than 180 consecutive days;
B. Be fully licensed and ready for highway use; or
C. Meet the elevation certificate requirements of § 156.052(b)(1), and the elevation and anchoring requirements for manufactured homes in division (d) above.
(2) A recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions.
(f) Crawl space. New construction and substantial improvements built on a crawl space or sub-grade (below-grade) crawl space may be permitted if the development is designed and meets or exceeds the standards found in FEMA's Technical Bulletins 1, 2, and 11, which include but are not limited to the following:
(1) The structure must be affixed to a permanent foundation, designed and adequately anchored to resist flotation, collapse, and lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. Because of hydrodynamic loads, crawl space construction is not allowed in areas with flood velocities greater than five feet per second unless the design is reviewed by a qualified design professional, such as a registered architect or professional engineer.
(2) The crawl space is an enclosed area below the BFE and, as such, must have openings that equalize hydrostatic pressures by allowing the automatic entry and exit of floodwaters. The bottom of each flood vent opening can be no more than one foot above the LAG.
(3) The crawl space enclosure must have proper openings that allow equalization of hydrostatic pressure by allowing automatic entry and exit of floodwaters. To achieve this, a minimum of one square inch of flood opening is required per one square foot, or smaller openings if they are approved engineered openings of the enclosed area subject to flooding.
(4) Portions of the building below the BFE must be constructed with materials resistant to flood damage. This includes not only the foundation walls of the crawl space used to elevate the building, but also any joists, insulation, piers, or other materials that extend below the BFE. Ductwork, in particular, must either be placed two feet above the BFE or sealed from floodwaters.
(5) Any building utility systems within the crawl space must be elevated above the BFE or designed so that floodwaters cannot enter or accumulate within the system components during flood conditions.
(6) The interior grade of a crawl space below the BFE must not be more than two feet below the LAG.
(7) The height of the below-grade crawl space, measured from the lowest interior grade of the crawl space floor to the bottom of the floor joist of the next higher floor cannot exceed four feet at any point.
(8) There must be an adequate drainage system that removes floodwaters from the interior area of the crawl space. The enclosed area should be drained within a reasonable time after a flood event.
(9) Buildings with below-grade crawl spaces will have higher flood insurance premiums than buildings that have the preferred crawl space construction with the interior elevation at or above the LAG.
(1992 Code, § 45-20) (Ord. 70-09, passed 8-3-2009; Ord. 85-11, passed 11-14-2011; Ord. 94-16, passed 8-2-2016; Ord. 78-17, passed 8-15-2017; Ord. 77-21, passed 7-6-2021)